Apple TV cuts off from Airport express

I do powerpoint presentation in places where there is no high speed internet. To be able to stream my presentation from my iPad or Computer I use a combination of Airport express to create a WiFi zone in my room, then I use Apple TV to connect to the Flat screen or projector. When my Computer, iPad, and Apple TV are all connected to the same WiFi zone the Airport Express created then I can stream my Power Point with out any hassle with wires.

My problem is that it works fine at the beginning and then suddenly the apple TV drops the signal and all the 'floating' back ground of Apple TV starts showing on the screen.

Is there some setting that will stop that from happening. If I move rapidly from slide to slide it keep connected OK, but if I stop for a couple of minutes I loose connection.